Acute psychiatric services--the emergency and inpatient services charged with responding to individuals and communities at times of psychiatric crisis--play important, but poorly understood, roles in community mental health systems. Emergency and inpatient psychiatric service use imposes high personal costs on service users and high financial costs on service systems. While evidence on acute psychiatric care is limited, there is compelling evidence of racial/ethnic differences and disparities in utilization. Available descriptive data on racial/ethnic differences and disparities does not provide explanations that can inform programmatic or policy changes to improve services and eliminate disparities. It is increasingly clear that a full understanding of racial/ethnic disparites in acute psychiatric service use necessitates moving beyond descriptive study of individual service users to consider the ways in which mental health system and community characteristics influence disparities. By explicitly examining system and community characteristics, we can begin to explain and address differences and disparities by identifying contexts and conditions that both increase and decrease them. The proposed project examines disparities in acute psychiatric service using a framework that considers race/ethnicity in the context of service system and community characteristics over time. Client-level Medicaid mental health claims data on over one million adults served in California's diverse county-operated community mental health systems since 2005 will be used to address three aims. First, quantitative methods will be used to test the hypotheses that there are racial/ethnic disparities in utilization of acute and outpatient psychiatric, but that outpatient service use is associated with reductions in acute service use disparities. Second, quantitative methods will be used to test the hypotheses that county-level investments in mental health services are associated with acute service use disparities and that economic downturns are associated with increases in disparities. Third, a mixed methods approach to county-specific analysis will characterize service strategies that reduce racial/ethnic disparities in acute psychiatric service use.